From a point of view of protection of a driver and/or a passenger in a car, an air bag apparatus which is a passenger protection apparatus has conventionally widely been used. The air bag apparatus is equipped for the purpose of protecting a driver and/or a passenger against shock caused at the time of collision of a vehicle, and it receives a body of a driver or a passenger with an air bag serving as a cushion, as the air bag is expanded and developed instantaneously at the time of collision of the vehicle.
The gas generator is equipment which is incorporated in this air bag apparatus, an igniter therein being ignited in response to power feed through a control unit at the time of collision of a vehicle to thereby burn a gas generating agent with flame caused by the igniter and instantaneously generate a large amount of gas, and thus expands and develops an air bag.
Gas generators of various structures are available. A disc type gas generator of which outer geometry is in a substantially short columnar shape is available as a gas generator suitably used for an air bag apparatus on a driver's seat side, and a cylinder type gas generator of which outer geometry is in a substantially long columnar shape is available as a gas generator suitably used for a side air bag apparatus, a curtain air bag apparatus, an air bag apparatus on a passenger's seat side, and a knee air bag apparatus.
A structure in which an igniter is fixed to a housing through insert molding of a resin material as a source material may be adopted for a gas generator in recent years from a point of view of reduction in weight and facilitation of manufacturing. Specifically, for example, for a disc type gas generator, such a structure has been adopted that a cylindrical lower shell with bottom having an opening formed in a bottom plate portion is fabricated by press-working one plate-shaped member made of metal, an igniter is arranged to pass through the opening, and a resin molding is formed by feeding an insulating fluid resin material into a space between the igniter and the lower shell and solidifying the resin material, so that the igniter is fixed to the lower shell with the formed resin molding.
Documents disclosing such a structure include, for example, Japanese Patent Laying-Open No. 2001-165600 (PTD 1), Japanese Patent Laying-Open No. 2010-173559 (PTD 2), and Japanese National Patent Publication No. 2012-504073 (PTD 3).
In order to obtain high gas output in an early stage from start of activation in a gas generator, it is important to efficiently guide thermal particles (that is, flames) generated in the igniter to the gas generating agent (to an enhancer agent when the enhancer agent is arranged between the gas generating agent and the igniter). Therefore, by arranging some member to surround the substantially columnar ignition portion of the igniter charged with the ignition agent, a direction of travel of the thermal particles generated in the igniter may be narrowed so that directivity is provided to the thermal particles.
For example, the gas generator disclosed in PTDs 2 and 3 is constructed such that substantially the entire outer circumferential surface of the ignition portion is covered with a thick resin molding and the resin molding in this portion provides directivity to a direction of travel of thermal particles generated in the igniter.